In recent years numerous attempts have been made to extract the vast quantities of energy that are contained in the oceans' waves. The studies by Gerstner in the early 1800's described the vast quantities of energy available and postulated the mechanisms by which such waves were formed. The most uniform waves are what are known as "deep ocean" waves which tend to exhibit a very constant wave by which is meant generally uniform wave height, generally a constant direction of motion of the undulating surface action of the waves, and constant spacing between wave crests characterizing a constant period of motion. The constant period of motion is also referred to as frequency and is determined by the length of time that it takes the crest or highest point of the wave to pass a fixed point in space and continuing until the next wave crest is encountered. The second wave crest is encountered only after a low point called the trough has passed the fixed point. The height of a wave is considered as the vertical distance between the water surface in the trough and the water surface of the crest and is twice the amplitude of a sine wave which such constant wave form substantially approximates. The period of a wave is measured in time; as, for example, a 10 second wave is a wave in which the period is equal to 10 seconds or 6 waves per minute pass a fixed point in space. Wave height is measured in units of length, feet or meters. For convenience, deep ocean waves are approximated as sine waves since the driving effects of the wind that originally formed them has long since been dampened and approximately sinusoidal undulation of the surface is observed with a relatively constant period and constant wave height.
Many waves found in shallower bodies of water or in the areas near the shore also demonstrate a substantially constant wave form, the relative distance between wave crests being essentially constant for long periods of time when observed and measured at a specific location. Therefore, such waves although containing less energy than deep ocean waves are clearly suitable for exploitation by wave following and other energy extraction apparatus.
Several types of devices have been developed for the removal of this energy store from waves. These include wave followers which are generally of the rack and pinion or of the piston operated energy extraction devices mounted on floats. The motion of the mechanical energy conversion device is caused by the rise and fall of the wave. In this way, the motion of the device "follows" the actual vertical movement of the wave under the float. Therefore, in a wave following device, the only significant forces which are exerted on the piston are the vertical forces of buoyancy and gravity.
The typical apparatus for use in converting the energy of ocean waves into a useful power form, is the wave following type flotational devices which has a structure disposed upon the water surface and supported by two floats and in turn having a third float associated with the structure. The third float is the energy conversion device itself and such a wave following type structure operates with the two support floats being placed apart from each other in such a way that when one support float was at a wave crest, the other support float was at a wave crest and correspondingly when one support float was in a wave trough, the other support float was in a wave trough. The energy conversion float is located intermediate the two support floats. The other consequential effect of such spacing of the support floats was that when one support float was descending from a wave crest, the other support float was also descending from a wave crest. The work extractable by any device is defined as a force operating through a distance. In the case of a wave following device, the distance is defined by the wave height and the force by the buoyant force of a float floating on the surface of the water, rising and falling in response to the undulation of the wave and the forces of gravity.
An inherent limitation of said devices is that the total buoyant force can only be increased by an amount related to the volume and mass of the float. The only other facet of the work equation that can be modified is stroke length and this is limited to twice the wave height by the design of the structure.
Therefore, there is a need for an improved wave following type energy conversion device to more efficiently and beneficially extract the available energy from ocean waves, most specifically those ocean waves occurring near the shore.